The invention relates to a friction roller for a device for open-end friction spinning of the type which includes a cover surface that forms a yarn formation zone and in the region of this yarn formation zone exhibits an outer surface structure which deviates from the plane of rotation (concentric surface about the axis of rotation).
It is disclosed in German Published Unexamined Application DE-OS No. 33 23 189 to provide the cover surface of a friction roller with a spirally extending outer surface texture in which the areas between the respective textured regions are left respectively untextured. The spirally extending textured strips exhibit a very small inclination so that approximately a ring texture is achieved. These measures are disclosed as being for the purpose of attenuating the friction forces opposite the yarn withdrawal direction in the axial direction of the roller so that the danger of disconnection of the yarn tip is reduced.
The invention is based upon the problem to improve a friction roller of the above-mentioned kind so that a higher consistency in the spinning condition and the resulting spinning results is achieved.
This problem is solved according to preferred embodiments of the invention by providing that the roller yarn forming surface texture is aligned essentially in the longitudinal direction of the cover surface of the roller.
Practical tests have surprisingly shown that the friction rollers, which after a long spinning time are hardly capable of spinning because of changes in the surface in the region of the yarn formation zone, can be made to be further capable of acceptable spinning by means of an upper surface treatment so that a yarn forming surface texture is achieved which is aligned essentially in the longitudinal direction of the cover surface.
In further development of especially preferred embodiments of the invention it is provided that the outer surface texture is formed as a plurality of microchannels extending essentially in the longitudinal direction of the friction roller cover surface. It has been determined that these kind of microchannels, which are hardly visible with the naked eye, result in an essential improvement.
According to a first embodiment it is provided that the outer surface texture is formed as a spiral extending at a sharp or accute angle with respect to the longitudinal axis of the roller. A spiral shaped outer surface texture of this type is preferably made through a corresponding treatment whereby the more acute the angle between the longitudinal axis and the spiral is the more advantageous for the spinning results. According to a further preferred embodiment of the invention it is provided that the outer surface texture is aligned parallel to the longitudinal axis of the roller. It has been shown that with this form of aligned outer surface texture, the best results are achieved.
In further developments of the invention there is provided a process for preparing a friction roller in which the rollers, at least in the region of the yarn formation zone, are treated by a grinding and/or polishing and/or brushing treatment, which treatment is essentially aligned to the longitudinal direction of the roller. In order to achieve an outer surface structure in the form of microchannels aligned parallel to the longitudinal axis of the roller it is provided according to the further development of the invention that the rollers are stopped during the treatment and that the rollers are step-wise turned between the respective treatment steps, which treatment steps extend essentially in the longitudinal direction of the roller.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment/several embodiments in accordance with the present invention.